System including a cathode ray display tube for providing a visual indication of a plurality of characters



Oct 7, 1970 D. G. GUMPERTZ 3,537,097 SYSTEM INCLUDING A CATHODE RAY DISPLAY TUBE FOR PROVIDING A VISUAL INDICATION OF A PLURALITY OF CHARACTERS Filed Jan. 2, 1968 2 Sheets-Sheet 1 A L7 INVENTOR.

77 fiat/Aw 6.6mm:

Oct. 27, 1970 D. G. GUMPERTZ 3,537,097

SYSTEM INCLUDING A CATHODE RAY DISPLAY TUBE FOR PfiOVIDING A VISUAL INDICATION OF A PLURALITY OF CHARACTERS Filed Jan 2, 1968 2 Sheets-Sheet 3 3 Q E m Z 7 Rm MP WW W6 mg w M v: B

llnited States Patent U.S. Cl. 340-324 18 Claims ABSTRACT OF THE DISCLOSURE A cathode ray display tube operating on the shadowgraph principle adapted for the simultaneous display of a plurality of characters. A plurality of individual electron beam sources are provided within the tube envelope, each source being mechanically directed at a common point on a fluorescent display screen. A mask having a number of shaped apertures, each aperture being associated with a different source is interposed between the sources and the display screen. Electrostatic or electromagnetic means for deflecting the electron beam away from the common point are located between the mask and screen. A plurality of sources are energized per unit time in synchronism with the deflection means to produce a simultaneous display of a plurality of characters on the screen.

CROSS REFERENCE TO RELATED APPLICATIONS The present application is related to my copending application Ser. No. 650,561, filed June 8, 1967 (Pat. 3,432,710, issued Mar. 11, 1969).

BACKGROUND OF THE INVENTION The present invention relates to cathode ray display tubes and in particular to a cathode ray tube capable of providing a simultaneous display of a plurality of characters on the tube display screen.

'In the above-identified patent application there is dis closed a cathode ray display tube having a plurality of individual electron sources or guns located and positioned within the tube envelope such that each of the sources is mechanically aimed along converging axes which meet a common point on a fluorescent display screen at the end of the tube opposite the location of the sources. Interposed between the sources and the display screen is a character forming mask having a plurality of apertures therein, each of the apertures having the outline of a different one of a selection of characters to be presented on the display screen. The number of characters in the selection corresponds to the number of electron guns provided within the tube. The mask is positioned between the guns and the display screen and the apertures are located in the mask such that each aperture is located on a different one of the source-screen axes whereby energization of a particular source produces the display of a particular associated character on the display screen.

The location of the mask and the size of the character forming aperture are chosen such that after a stream of electrons from a selected source illuminates an aperture, forming the stream into a specific outline, the stream expands in transit toward the screen such that ice the image projected thereon is centered on and substantially fills the screen.

Such a display tube is readily adapted for applications where heretofore backlighted incandescent display units and multifilament tubes such as Nixie tubes have been used for providing a digital readout. Where a multicharacter readout is required, a number of cathode ray display tubes corresponding to the maximum number of digits possible is provided. By connecting suitable decoderdriver circuitry to the :various tubes a preselected one of the plurality of sources in each of the tubes is energized at any one time to produce the desired multicharacter readout.

By the present invention an improvement over the above-described cathode ray display tube is provided. The invention comprises a vacuum tube display device for selectively presenting at least one of a selection of patterns on a screen, including an evacuated envelope having a display screen at one end with the screen having a fluorescent coating on the interior thereof. A plurality of electron sources are located within the envelope, each source including electrode means for directing a diverging stream of electrons toward the screen along a line extending from the source and passing through a common point on the screen. Means for selectively operating each of the electron sources to release a stream of electrons from at least one of said sources are connected to each one of said electrode means. A mask is provided which is located between the electron sources and the screen having openings therein in the form of the selection of patterns to be displayed. Each of the openings in the mask is aligned on a different one of the lines between the electron sources and the common point such that each source illuminates only the opening in said mask associated with that source. Electrode means for accelerating the released stream of electrons toward the mask and screen are located between the electron sources and the mask. Electron stream de flection means are also provided with the tube and are located intermediate the geometric planes defined by the mask and the display screen for deflecting the stream of electrons away from the source-screen axis such that when the deflection means is energized the character projected by the device on the screen is centered on a point removed from said common point on the screen.

In comparison with the cathode ray display apparatus of the prior art and the elaborate deflection and intermediate focusing systems characteristic of multicharacter readout versions of such apparatus, the present invention provides a cathode ray display tube utilizing simplified deflection means which when operated deflect the shaped electron beam away from an aiming point common to all of the electron sources of the display tube. By locating a character forming mask at an appropriate position along the length of the tube, restricting the size of the character forming apertures in the mask to a predetermined size and providing suitable sweep circuitry, a plurality of characters fanned out in a horizontal, vertical, or combined pattern, can be displayed on the screen simultaneously. In this manner, the need for a plurality of the devices described in the aforementioned patent application for providing the readout of a combination of characters is eliminated.

It is contemplated that among many other applications for the present invention, wide application [will be found in various types of analytic and measuring instrumentation, e.g., digital volt meters. In addition, other applications include many of the myriad variety of calculators and computers, as well as counters and display panels.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will be better understood by reference to the following figures wherein:

FIG. 1 is a plan view of a display tube according to the present invention;

FIG. 2 is an elevational view taken along lines 22 of FIG. 1;

FIG. 3 is an elevational view of an alternate embodiment of the invention;

FIG. 4 is a schematic diagram depicting one embodiment of electrical circuitry associated with the display tube of the present invention;

FIG. 5 is a Wave form diagram illustrating one cycle of operation of the tube of FIG. 1; and

FIG. 6 is an elevational view of another alternate embodiment of the cathode ray tube according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a multisource cathode ray display tube which utilizes a plurality of shaped apertures interposed between the sources and the display screen of the tube to shape an electron stream emitted by a particular source into the outline of the aperture. Each source is arranged so as to direct a diverging stream of electrons toward the screen along a line or axis extending from each source and passing through a common point on the screen. The shaped stream is then selectively subjected to the effect of electrostatic or electromagnetic deflection means located between the planes defined by the electron beam shaping apertures and the display screen to control the position on the display screen where the image is displayed. The shaped electron beam retains the outline of the aperture through which the beam is passed in its transit to the display screen Without distortion whether subjected to deflection or not.

Typically the deflection of the electron beams is accomplished by locating at least one electromagnetic coil between the two aforementioned planes and supplying electrical energy thereto. Under the influence of the magnetic field created by the coil, the electron beam which would otherwise be displayed at a location centered about the common point on the screen, normally the center of the tube, is displayed at a location removed from this point. Deflection can also be accomplished electrostatically with the electromagnetic coil being replaced by at least one electrode connected to a source of high voltage. When voltage is supplied to the electrode, the electric field associated with the electrode exerts a force on the shaped electron beam deflecting it away from the point at which it is normally mechanically aimed.

In a preferred embodiment the deflecting means are provided in balanced pairs, i.e., pairs of electromagnetic coils or electrodes, to eliminate distortion of the image displayed on the screen. With balanced deflection the only change in the physical dimensions of the shaped electron beam is that the beam continues to diverge without any change in one portion of the shape relative to other portions of the shape.

'In one embodiment, as shown in FIGS. 1 and 2, a display tube 10 having a rounded dome as shown in FIG. 1 or a flat face is provided on a mounting base 12, the entire assembly being secured by a base plate 14 and side supports 16 so as to be centered in a window 18. Disposed above and below the display tube 10 are electromagnetic coils 19 and 20, respectively, which, when connected to a source of electric power (not shown), produce deflection of the electron beam within the display tube as will be described more fully below.

As shown in FIG. 2, this embodiment of the display tube is capable of producing a simultaneous display of at least three characters 22, By locating the magnetic coils 19 and 20 above and below the tube and energizing said coils with a current flowing first in one direction in the coils and subsequently in an opposite direction, deflection of the electron beam Within the tube to the right and to the left is accomplished. By providing suitable sweep circuitry for energizing any three electron sources within the tube per unit time and synchronizing the energization of the magnet coils with the energization of the electron source, three characters are displayed simultaneously on the screen in a horizontal pattern.

Both the natural persistence of the viewers eye and the finite decay time of conventional phosphors used in the fluorescent screen contribute to the impression that utilized without producing any sensation of decay or darkening of image. To prevent flicker, the guns providing the three digit display are energized at a frequency not less than 20 cycles per second to take advantage of the persistence of the human eye. By providing phosphors of still greater persistence, the duty cycle can be reduced further enabling the simultaneous display of an increased number of characters without any detectable deterioration of the displayed image. In the same manner, location of a set of electromagnetic coils to the right and to the left of a display tube produces deflection of the electron beam in a vertical direction. Again, with suitable sweep circuitry, simultaneous display of a character above and below the character produced in the center of the screen can be accomplished.

In FIG. 3 electrostatic deflection means are illustrated comprising electrodes 15 and 17 which are connected to a source of voltage (not shown). As shown in FIG. 3, a directly heated filament 13 is suspended between supports (not shown). Disposed along the vertical length thereof are a plurality of electron source enclosures 21, each of the enclosures having apertures 23 in the side thereof adjacent a display screen 25. When filament 13 is heated electrons are generated within each of the source enclosures. The electrons are confined within the enclosures by maintaining a negative potential on them through the imposition of a negative voltage on a grid as described in Pat. 3,432,710 issued to me on Mar. 11, 1969. Upon applying a positive voltage to the grid in one or more selected enclosures as described in Pat. 3,432,710, electrons pass through aperture 23 and another corresponding aperture in accelerating enclosure 27. A beam shaping mask 29 is interposed in the path of the electron beam, the mask having a plurality of shaped apertures 31 for shaping the stream of electrons into the outline of the character which it is desired to display on the screen. One or more masks 33 may be interposed between the end of accelerating enclosure 27 and the beam shaping mask 29 for purposes of limiting the cross section of the stream incident on the character shaping mask.

The display tube of FIG. 3 illustrates the Way in which three characters can be displayed simultaneously on screen 25 in a vertical orientation. By connecting sweep circuitry to the enclosures 21, synchronizing the applica tion of deflecting voltage to electrodes 15 and 17 and controlling the direction of the electric field created between electrodes 15 and 17, a character can be displayed at the top, in the center and at the bottom of display screen 25. This is accomplished by first applying electric voltages to the deflecting electrodes with the direction of the field being from electrode 17 toward electrode 15. When the second gun is energized no deflecting voltage is applied to the deflecting electrodes. When the third gun is energized an electric field is created between the electrodes directed from electrode toward electrode 17.

One embodiment of sweep circuitry for driving the tube illustrated in FIGS. 1 and 2 is shown in FIG. 4. Information or data to be displayed on the face of the cathode ray tube is transmitted over three groups of leads represented by input leads 24 to a logic circuit 26. The logic circuit is also provided with a commutator device which, in conjunction with circuitry for energizing the electromagnetic deflection coils, energizes one or more of the electron guns within the tube in accordance with the signals presented by each data group during each cycle of tube operation to produce a three digit readout. The energizing signals from the logic circuit 26 are transmitted to the display tube control grids over one or more of the ten output leads 28 from circuit 26 to turn on the desired sources in the desired sequence.

Energization of the deflection coils is provided by means of a-multivibrator 30 whose output is connected to a divider network 32 which in turn is provided with two output leads 34 and 36. Divider network 32 is arranged such that for every three pulses transmitted to it by the multivibrator, two pulses are retransmitted by the network. In a typical sequence, the divider transmits the first pulse over lead 34, then attenuates the second pulse transmitting nothing and subsequently transmits the third pulse over lead 36. A signal transmitted by divider network 32 over lead 34 is transmitted to an amplifier 38 which directs current through deflection coil 19 in a first direction. The same signal is transmitted over lead 34 to logic circuit 26. A signal is then transmitted over one of the leads 28 to the appropriate electron source enclosure or control grid of the display tube producing a character display at one side of the screen, e.g., the numeral 1 as shown in FIG. 2. With no output from divider network 32 there is no energization of the deflection coils. The commutator in logic circuit 26 detects the grid to be energized from the signal on the second of the three groups of input leads and provides an output over one of the leads 28 causing the tube to direct an undeflected beam of electrons at the center of the display screen, producing, for example, the number "4 shown on the face of the tube in FIG. 2. Current directed through the deflection coils in the opposite direction, i.e., from amplifier 40, produces a second character display on the other side of the screen, e.g., the numeral 7 in FIG. 2.

One cycle of operation of a three digit display tube is illustrated in FIG. 5. The solid trace 42 corresponds to the signal transmitted to the deflection coils and the broken trace 44 corresponds to the signal transmitted to one of the enclosures or grids of the display tube. When current is passed through the deflection coils in one direction corresponding to the positive going portion of trace 42 a character is displayed on the tube which is deflected to the left of center of the tube. To allow for the inductive effect of the coils, a small amount of delay designated by reference numeral 46 may be introduced between the energization of the coil and the energization of the grid of the display tube to prevent smearing of the image.

As the next pulse from the multivibrator no deflection signal is produced and a stream of electrons is directed at the face of the screen without deflection producing a readout in the center of the tube. At the next output from the multivibrator, a pulse corresponding to the negative going portion of trace 42 isdirected through the deflection coils causing current to flow in the coils in the direction opposite from that of the preceding energization of the coils thereby producing a deflection of the electron beam to the right of center of the tube face. Provided this cycle is repeated a minimum of twenty cycles per second, a flickerless, three digit display is produced on the face of the tube. As the input on any of the three input leads 24 changes, the character display on the face of the tube changes correspondingly.

To provide for the simultaneous display of more than three characters, the current through the coils or the voltage supplied to deflecting electrodes is supplied in stepped increments to produce varying amounts of deflection of the electron beam corresponding to the posi tion of each character place on the face of the tube relative to that of the other character places. The number of pulses generated by the sweep circuit for each cycle of operation of the tube is arranged to produce the number of characters which are to be displayed simultaneously.

In still another alternate embodiment deflection means 48 are provided on four sides of the tube as shown in FIG. 6. The tube face in this embodiment is enlarged to permit the display of a number of alphanumeric characters on the face of the screen. To accomplish the display such as illustrated in FIG. 6, a sweep circuit is provided having a relatively high frequency of operation. Deflecting currents or voltages are supplied to the various deflection means in stepped increments and in predetermined combinations to produce a display such as the sixteen digit display on the face of the tube shown in FIG. 6.

In such applications as digital voltmeters and certain types of calculators a single horizontal line of characters is required to provide the readout from the instrument. The present invention readily lends itself to such an application. By providing a tube of the width of the tube shown in FIG. 6, capable of providing a readout of one of the lines of the four shown in that figure, a single horizontal line of characters can be displayed. A sweep circuit is then provided generating the number of pulses per cycle needed to produce the desired number of character places to be displayed on the screen. A deflection circuit sequentially supplies the electrical signals to deflection means in synchronism with the sweep circuit pulses to locate the characters in their proper position on the screen.

What is claimed is:

1. A vacuum tube display device for selectively presenting on a visual basis at least one of a selection of patterns, including:

an evacuated envelope having a display screen at one end, the screen having a fluorescent coating on the interior thereof;

a plurality of electron sources located within the envelope each source including electrode means for directing a diverging stream of electrons toward the screen along a line extending from the source and passing through a common point on the screen;

means connected to each of said electrode means for selectively operating each of the electron sources to release a stream of electrons from at least one of said sources;

a mask located between the electron sources and the screen and having openings in the form of the selection of patterns to be displayed, each of said openings being aligned on a different one of the lines between the electron sources and the common point such that each source illuminates only the opening in said mask associated with that source;

electrode means located intermediate the electron sources and mask for accelerating the released stream of electrons toward the mask and screen;

first electron stream deflection means associated with the tube and located intermediate the planes defined by the mask and the display screen for deflecting the stream of electrons in a first particular direction displaced from the common point on the screen such that when the deflection means is energized the character projected by the device on the screen is centered on a point removed from said common point on the screen; and

first control means operatively coupled to the first electron stream deflection means for intermittently changing the operation of the deflection means to obtain a deflection in the first particular direction of the stream of electrons different from the previous deflection of the stream of electrons.

2. A display device according to claim 1 wherein the deflection means includes at least one electromagnetic coil.

3. A display device according to claim 2 wherein the deflection means includes a pair of electromagnetic coils, the coils being located on opposite sides of the display device for deflecting the electron stream in a direction transverse to a plane passing through the coils.

4. A display device according to claim 1 wherein the deflection means includes at least one electrode.

5. A display device according to claim 4 wherein the deflection means is a pair of electrodes located on opposite sides of the display device for deflecting the electron beam in a direction substantially parallel to a plane passing through the electrodes.

6. A display device for selectively presenting a plurality of patterns on a fluorescent display screen, including:

a plurality of electron guns mechanically aimed at a particular position on the fluorescent display screen, each gun including electrode means for directing a diverging stream of electrons along an axis extending from the gun and passing through a common point on the screen;

a mask located between the electron guns and the display screen and having openings in the form of a selection of patterns to be displayed, each of the openings being disposed to provide for the passage of the electrons from an individual one of the guns in the plurality through the opening;

first deflection means located between the mask and the display screen for deflecting the electron stream from any one of said electron guns in a particular direction to a position displaced from the common point on the gun screen;

means connected to each of said electrode means for selectively energizing each of said electron guns to obtain a direction of the stream of electrons toward the screen; and

first sweep circuit means connected to said energizing means and said deflection means for periodically operating a preselected number of electron guns per unit time and periodically operating the deflection means to provide progressive deflections of the electron stream in the particular direction in substantial synchronism with the operations of the electron guns whereby a simultaneous display of at least two characters is provided on the display screen.

7. A display device according to claim 6 including means for varying the electric energy supplied to the first deflection means in accordance with the successive operation of the guns for varying the amount of deflection imparted to the electron stream upon each successive operation of the guns.

8. A display device according to claim 6 wherein the first deflection means are arranged so as to deflect the electron streams in a substantially horizontal direction.

9. A display device according to claim 6 wherein second deflection means are arranged to deflect the electron streams in a substantially vertical direction.

10. A display device according to claim 6 wherein the first deflection means and second deflection means are located relative to the electron streams and to one another for producing a display having a plurality of rows and columns of characters.

11. The display device set forth in claim 1 wherein the control means is operative to displace the stream of electrons through progressive positions in the particular direction.

12. The display device set forth in claim 1 wherein second electron stream deflection means are associated with the tube and located intermediate the planes defined by the mask and the display screen and transverse -to the direction of deflection produced by the first electron stream deflection means for deflecting the stream of electrons, in a second particular direction transverse to the first particular direction, away from the source-screen line and wherein second control means are operatively coupled to the second electron stream deflection means to obtain a deflection in the second particular direction of the stream of electrons difierent from the previous deflection of the stream of electrons.

13. The display device set forth in claim 12 wherein the first control means is operative to displace the stream of electrons through progressive positions in the first particular direction on a cyclic basis and wherein the second control means is operative to displace the stream of electrons through progressive positions in the second particular direction on a cyclic basis and wherein the second control means is operative to displace the stream of electrons through a progressive position in the second particular direction upon each completion of a cycle 'by the first control means.

14. The display device set forth in claim 6 wherein second sweep circuit means are associated with the tube and located between the mask and the display screen and transverse to the direction of the deflection produced by the first sweep circuit means for deflecting the stream of electrons, in a second particular direction transverse to the first particular direction, to a position displaced from the common point on the screen.

15. The display device set forth in claim 6 wherein the first sweep circuit means are operative to displace the stream of electrons in the particular direction through progressive positions on a cyclic basis.

16. The display device set forth in claim 6 wherein second sweep circuit means are associated with the tube and located between the mask and the display screen and transverse to the direction of the deflection produced by the first sweep circuit means for deflecting the stream of electrons, in a second particular direction transverse to the first particular direction, to a position displaced from the common point on the screen and wherein the second sweep circuit means are operative to displace the stream of electrons in the particular direction through progressive positions on a cyclic 'basis with each displacement occurring upon the completion of a cycle of displacements by the first sweep circuit means in the first direction.

17. A display device for selectively presenting a visual display of a plurality of patterns, including first means for providing a stream of electrons;

a fluorescent display screen displaced from the first means;

a mask located between the first means and the display screen and having a plurality of openings at displaced positions on the screen in the form of a selection of a plurality of different patterns to be displaced;

second means operative upon the first means for directing a stream of electrons selectively through individual openings in the plurality on the mask to provide for a visual display of individual patterns in the plurality;

deflection means located between the mask and the display screen and constructed to be energized at different levels for deflecting the electron stream in a particular direction in accordance with the level at which the deflection means is energized;

third means for providing progressive periods of time and for distinguishing these .periods of time from one another;

fourth means operatively associated with the second and third means for providing a passage of the stream of electrons through individual ones of the openings in the mask in each of the progressive periods in accordance with the individual ones of the patterns to be visually displayed in each of the progressive periods; and

fifth means operatively associated with the deflection means and the third means for progressively energizing the deflection means in each of the progressive periods to obtain a deflection of the stream of electrons progressively in the particular direction.

18. A display device as set forth in claim 17 wherein the third means are operative to distinguish the progressive periods of time from one another on a cyclic basis to provide a repetitive sweep of the stream of electrons on a cyclic basis in the particular direction.

References Cited UNITED STATES PATENTS 2,761,988 9/1956 McNaney 313-69 2,862,144 11/1958 McNaney 31369 X JAMES W. LAWRENCE, Primary Examiner V. LAFRANCHI, Assistant Examiner U.S. Cl. X.R. 

